There are many processes and techniques today for gas-assisted injection molding. Gas-assisted injection molding processes have added new flexibility to the design and manufacture of plastic parts with their ability to produce partially hollow, lightweight, rigid parts with minimal sink marks and less tendency to warp. These processes can reduce material requirements, as well as equipment costs and cycle time, and thus have advantages over conventional injection molding processes and techniques in many applications.
In general, gas-assisted injection molding systems utilize a fluid or gas, such as nitrogen, under pressure to expand the plastic material in the mold and conform it to the mold cavity details. The fluid or gas can be introduced into the mold in several ways, such as through a bushing, nozzle, or machine nozzle in one or more cavities, or in more than one location.
With gas-assisted injection molding techniques, care must be taken to ensure that the gas delivery orifices into the mold do not become plugged or clogged with plastic material and, at the same time, it is necessary that the gas be directed into the mold cavity and not back into the bushing, runner system, or plastic injection system.